Soft washing explained, in plain English

A biocidal solution is applied evenly to the surface at roughly garden-hose pressure. The solution kills algae, lichen and moss at the root and breaks down the biological film that gives tiles and render that dull green-black cast.

Nothing is stripped away by force. The dead organic material then weathers off over the following weeks and months, helped along by ordinary rainfall. On lighter surfaces a gentle rinse finishes the job; on roofs we usually leave the weather to do it.

Pitched roofs of every common covering, including concrete interlocking tiles, clay plain tiles and pantiles, natural slate, fibre cement and even fragile older coverings that could never take mechanical cleaning.

Rendered walls, painted masonry, K-Rend and other silicone systems, uPVC fascias, soffits, cladding, conservatory frames and roofs, and garden structures. Anywhere the finish is worth more than the dirt sitting on it, soft washing is the right method.

Render and uPVC usually look markedly better the same day, because the film is thin and can be rinsed gently once it has lifted. Roofs are slower. Expect the colour to keep improving for six to twelve weeks as the dead growth breaks down and washes off in the rain.

That gradual change is a sign the method is working correctly rather than a sign of a poor job. The trade-off for patience is a roof covering that is still intact at the end of it.

Solution strength is matched to the surface and the level of colonisation. Planting below the work area is sheeted or wetted down, glazing and paintwork are protected, and pets are kept indoors while the treatment is going on.

Our team is fully insured and uniformed, works from our own equipment and applies treatments from safe access rather than from a stretched ladder position. If the weather turns during the visit, we stop, because wind and rain both waste solution and put it where it is not wanted.